Lets say you have a toon named, "MMO1(main)", "MMO2(alt)".
Even if you check that option, by going to MMO2s profile page on guild ox and pressing the "update" button will add your alt to the list on the
MMO1 profile.

I have tested this a few minutes ago.
Not sure how guild ox is doing it, but checking the option is not working.
Maybe its tracking the achieves from "Recent Activity" on the armory, since I do have achieves I got an hour or two ago.

Let's say you have a database full of each achievement, and a timestamp when you first earned it.

All it takes now, assuming both characters have the same timestamps on each achievement is a quick query on the account bound stuff to find two records with exact matching dates across all characters for a given realm, from there you can make the assumption that if characters 1,2,3,4 all got achievements X,Y,Z on the same day, that they're the same person (as even members of a raid would have different time stamps on non-raid things)

EDIT:

Also, If someone's "Harassing" you, report them. removing websites that let you pinpoint alts is not the problem, the person threatening, idle threats, and rolling new alts to circumvent your ignore list (all of the above are against the TOS) is the problem. The website is an accessory, and nothing more.

Let's say you have a database full of each achievement, and a timestamp when you first earned it.

All it takes now, assuming both characters have the same timestamps on each achievement is a quick query on the account bound stuff to find two records with exact matching dates across all characters for a given realm, from there you can make the assumption that if characters 1,2,3,4 all got achievements X,Y,Z on the same day, that they're the same person (as even members of a raid would have different time stamps on non-raid things)

EDIT:

Also, If someone's "Harassing" you, report them. removing websites that let you pinpoint alts is not the problem, the person threatening, idle threats, and rolling new alts to circumvent your ignore list (all of the above are against the TOS) is the problem. The website is an accessory, and nothing more.

I just wanted to point out that, althought Guildox said one can avoid their alts being tracked if you check the "Display Only Character Achievements to Others", this is not true.
And I have tested it.
If your alts profile is currently up-to-date on Guildox's website, it will link your alts to your main.
Or, the person who wants to know if a specific character is your alt, they can just refresh it on Guildox.(Of course to do this, they need to have your alts character name)

Like I said in my original post, my main was already update and was on Guildox.
My alt wasn't. So I directly accessed my alt toon by entering, h t t p://www.guildox.com/wow/toon/us/(my alts server name)/(my alts toon name),
then refreshed it. After that, my Main and alt were linked.
This can be done by anyone. And I'll say again, the options "Display Only Character Achievements to Others" was checked for all of my toons.

So I just wanted to send out a warning that if you're feeling safe just by checking this option, you're not safe at all.

It is results of opened Pandora's Box with account-wide achievements, and it was already quite known how it will affect privacy in-game. Without having any proper option to completely opt out of it, there is no real possibility to remove tracking down.

It's just that people ain't much bothered with this kind of invasion of in-game privacy. CRZ and dailies, as new features, greatly outshine this.

Best solution would be to make Achievements to not be "inspectable" neither in-game nor on armory, by introducing some kind of such option. But I doubt such feature will ever be implemented no matter how people ask, as developers don't want to remove even CRZ, nevermind about adding option to hide achievements.

People saw this coming when the first version of armory came up. I never liked the activity feed.

Yes claiming your character and hiding your alts on those websites does work, but you'll need to do it for all of the website which provide that kind of feature.
But that doesn't really solve the basic problem, because if people have the knowledge to data mine WoW's armory, anyone can do it without using those websites.

So if you want this to be solved permanently, Blizzard has to do something about their armory.(not sure if its technically possible)

And like some other people are saying, its not the websites fault providing these features.
They're just using the data which Blizzard is making available to the pubic. Its not like they're hacking or exploiting the armory.
Thus if you consider this as a privacy issue, you should be contacting Blizzard instead.

If you're indeed scammed him for money, then your post looks like "can police track break this guy's camera - he caught me stealing on it!". I honestly don't understand why people even bother to give you workarounds. I hope YOU get permaban instead.

Yes claiming your character and hiding your alts on those websites does work, but you'll need to do it for all of the website which provide that kind of feature.
But that doesn't really solve the basic problem, because if people have the knowledge to data mine WoW's armory, anyone can do it without using those websites.

So if you want this to be solved permanently, Blizzard has to do something about their armory.(not sure if its technically possible)

And like some other people are saying, its not the websites fault providing these features.
They're just using the data which Blizzard is making available to the pubic. Its not like they're hacking or exploiting the armory.
Thus if you consider this as a privacy issue, you should be contacting Blizzard instead.

The WoW armory leaking tons of character data (which can then be data mined and correlated) is an intended feature and not a bug, unfortunately.

If you're indeed scammed him for money, then your post looks like "can police track break this guy's camera - he caught me stealing on it!". I honestly don't understand why people even bother to give you workarounds. I hope YOU get permaban instead.

A better analogy would be if he was filming on property that isn't his.

Personally it doesn't matter if in this instance they scammed someone out of gold, that does not mean they should be harassed, two wrongs don't make a right and harassing people is slightly higher on blizzards watch list than scamming of a virtual currency

If a website has the ability to be abused by people willing to commit this sort of behaviour they really should take it on themselves to prevent that.

Because if someone wants to harass you and you name change to get away from them, they just go on WoWTrack and they use your shared alt achievements to find your new name.

Last time I name changed, people who had me on their friends list had my new name added... and was getting messages asking who I was... so if someone was giving you hassle, chance are they have you on their friends list to see when you are on. But if you name change to get away from someone, wouldn't it be better to just report the other person for harassment?

I think this is quite over the top really. Looking at it, really, what privacy is invaded? It's not like anyone can show up at yor doorstep or anything. If you get harassed, report the person harassing you. Don't blame the tool but blame the person using it.
Guns don't kill people.... remember? Although, sinc eimpact is bigger I wouldn't mind seeing guns forbidden by law...

P.S. On thing I just though of... I wouldn't be surprised if Blizzard can use that data as they see fit. Because technically they still own the character and the player doesn't.
Then again, that's nitpicking.

Yes claiming your character and hiding your alts on those websites does work, but you'll need to do it for all of the website which provide that kind of feature.
But that doesn't really solve the basic problem, because if people have the knowledge to data mine WoW's armory, anyone can do it without using those websites.

The op is talking about wow track and not the other sites. So simply this fixes the problem for him.

It is results of opened Pandora's Box with account-wide achievements, and it was already quite known how it will affect privacy in-game. Without having any proper option to completely opt out of it, there is no real possibility to remove tracking down.

It's just that people ain't much bothered with this kind of invasion of in-game privacy. CRZ and dailies, as new features, greatly outshine this.

Best solution would be to make Achievements to not be "inspectable" neither in-game nor on armory, by introducing some kind of such option. But I doubt such feature will ever be implemented no matter how people ask, as developers don't want to remove even CRZ, nevermind about adding option to hide achievements.

Technically it's not a privacy issue. It doesn't reveal any of your personal data, only characters, and they are Blizzard property.

hey, i know this is really old post but i found it on google cus it was connected to wowtrack. I tried to search for my shaman there, but when i click on it, it goes to character called Melar and it looks like he have my achievements, does it mean that he connected his shaman to mine on that page to steal my progress in the game or is it some bugg? Cus i cant look directly on my shaman only.